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Math Help - what is the domain of this function

  1. #1
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    what is the domain of this function

    can anyone help tell me what the domain of this function is please

    f(x) = 1
    _________

    sqr root of (1-x)(7+x)
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  2. #2
    No one in Particular VonNemo19's Avatar
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    Quote Originally Posted by emmalou264 View Post
    can anyone help tell me what the domain of this function is please

    f(x) = 1
    _________

    sqr root of (1-x)(7+x)
    What makes f(x) undefined. ie What make the denominator 0, or what makes the radical undefined (negative)

    The domain is all values of x for which the function is defined.

    I'll give u one place that it's not defined.........

    x<-7

    here's another

    x>1

    here's another

    x=1

    here's another

    x=-7

    So are you familiar with interval notation?

    (-7,1)
    Last edited by VonNemo19; June 10th 2009 at 05:04 PM. Reason: Made a Boo Boo
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  3. #3
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    Quote Originally Posted by VonNemo19 View Post
    What makes f(x) undefined. ie What make the denominator 0, or what makes the radical undefined (negative)

    The domain is all values of x for which the function is defined.

    I'll give u one place that it's not defined.........

    x<-7

    here's another

    x>1

    here's another

    x=1

    here's another

    x=-7

    So are you familiar with interval notation?

    [-7,1]
    A square bracket means that the endpoint is included. A round bracket means that the endpoint is not included. So a slight correction to this answer is required: (-7, 1).

    @OP: Since (1 - x)(7 + x) > 0 is required, the interval is most easily found by drawing a graph of the parabola y = (1 - x)(7 + x) and looking for the values of x such that y > 0.
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  4. #4
    No one in Particular VonNemo19's Avatar
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    Quote Originally Posted by mr fantastic View Post
    A square bracket means that the endpoint is included. A round bracket means that the endpoint is not included. So a slight correction to this answer is required: (-7, 1).

    @OP: Since (1 - x)(7 + x) > 0 is required, the interval is most easily found by drawing a graph of the parabola y = (1 - x)(7 + x) and looking for the values of x such that y > 0.
    I simply cannot believe I did that. aaaaaaarrrrrrrrrrrrrrrrrgggggggggghhhhhhhhh!!!!!!! !!!!!!!
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